In systems such as motor vehicle air conditioning, heating and ventilating systems, one or more doors used therein to control air flow can require several pounds of force to effect their movement to a variable position. A Bowden wire because of its flexibility for ease of circuiting is generally desired for effecting this air door movement. However, the manual control force that is required can be prohibitive as it is desirous for example to not let such manual force exceed one pound.